Conventional scanning system can be approximately divided into two segments that are handy scanning system and flat-bed scanning system. A scanning system makes use of focusing a reflecting light beam through a photodetector to generate an image signal for further image processing. A conventional scanning system apparatus includes a light source, a mirror, and a lens set, which are used to guide the reflecting light to a charge couple device (CCD). The charge couple device is utilized to generate an image signal. A pre-processing element is used to respond an image signal and adjust dc gain of the image signal. An analogue to digital converter is used to convert adjusted image signal to a digital signal and a post-processing element to generate an image code by processing said digital signal through highlight, shadow, and Gamma correction.
Typically, image capture is achieved by passing the document in front of a device known as a CCD. This consists of a large of very small, individual semiconductor receptors, disposed in a linear array. The document is passed in front of the CCD and a complete image of the document linear segments individually captured from the CCD. The CCD consists of a semiconductor material which is formulated to convert incident light into an analogue electrical signal. The signal output by the CCD is subjected to shading correction, bit by bit, thereby providing image data. The shading correction comprises two steps. In the first step, the one-bit pixel data items defining an image are corrected based on the difference between the black reference signal and the white reference signal, thereby forming corrected image data. In the second step, the low frequency distortion and high frequency distortion occurring in the data-reading unit are minimized in accordance with the corrected image data.
In practicing the scanning system, the light source is reflected from the surface of a document, then it is reflected against from the mirror and focused by a lens set. The mirror and the lens set are used to guide the light beam to a CCD. Subsequently, the light beam is converted to an image signal by the CCD, and direct current (d.c.) gain of the image signal is adjusted by a pre-processing element, i.e. a d.c. gain voltage amplifier. Then the adjusted image is fed to an analogue to digital converter (ADC) for converting adjusted image signal to a digital signal. The digital signal is fed to a post-processing element to generate an image code by processing the digital signal through highlight, shadow, and Gamma correction.
However, in conventional scanning apparatus, the document is fed into the scanning apparatus by using rollers, which will cause the document is damaged by the rollers. Therefore, the output quality of the scanning system can not meet the requirement of the present demand. Further, the cost of the conventional scanning apparatus that is built in a computer is high and the structure of the apparatus is also complicated.